Bacterial translocation (BT) can be involved in the pathogenesis of severe infections due to bacteria of enteric origin that complicates bleeding cirrhotic patients. To assess the effect of hemorrhagic shock (HS) on the incidence of BT and if selective intestinal decontamination (SID) reduces this incidence, we studied six groups of Sprague-Dawley rats: ascitic rats, ascitic rats exposed to HS with and without previous norfloxacin prophylaxis, healthy rats, and healthy shocked rats with and without previous norfloxacin prophylaxis. BT tended to be higher in ascitic rats with shock than without shock (69% vs. 41%, P = .15) and was significantly higher in healthy rats with than without shock (50 percent vs. 0 percent, P = .01). Norfloxacin significantly reduced translocation in ascitic shocked rats in comparison with nondecontaminated ascitic shocked rats (31 percent vs. 69 percent, P = .038). This effect was due mainly to a reduction of gram-negative BT (O percent vs. 37 percent, P = .008). In addition, norfloxacin prevented translocation in healthy shocked rats. Accordingly, aerobic gram-negative bacteria disappeared from fecal flora in all rats administered norfloxacin, except for Klebsiella species in one control rat. Cecal severe submucosal edema, chronic inflammatory infiltrate, and intestinal lymphangiectasia were significantly more frequent in ascitic rats than in control rats. Intestinal mucosal injury related with HS, particularly subepithelial cecal edema, was observed only in ascitic shocked rats. In conclusion, HS increases the incidence of BT both in ascitic cirrhotic and healthy rats. Norfloxacin reduces significantly the incidence of translocation after shock, especially in those cases caused by aerobic gram-negative bacilli.